Transamination is a transfer of an amino group from one chemical compound to another, or the transposition of an amino group within a chemical compound. Transamination can be used to prepare amine compounds and mixtures of amine compounds from lower molecular weight nitrogen-containing compounds such as amines or nitriles. Transamination can provide acyclic and/or cyclic amine products. GB Patent No. 1508460 describes the transamination of ethylenediamine (EDA). U.S. Pat. Nos. 4,568,746 and 7,053,247 also describe the transamination of EDA. GB Patent No. 1551127 describes the transamination of 1,3-diaminopropane (1,3-DAP). JP 2006/306790 reacts 1,3-DAP with ethylene glycol in the presence of a dehydration catalyst such as activated alumina at 300C to obtain homopiperazine (hPIP) at 24% yield. The technical literature describes making hPIP from a mixture of EDA and 1,3-dibromopropane. See Huaxue Shiji, 2006, 28(5), 311-312. U.S. Pat. Nos. 6,465,601 describes the preparation of mixed amines by the transamination of a substituted phenolic compound (Mannich base) with another amine. The mixed amines are useful as accelerators for curable epoxy and polyurethane systems.
Although transamination has proved itself as a viable way to manufacture amines on the industrial scale, several challenges remain. First, the ability to customize product mixtures for desired end uses can be limited. Additionally, some processes produce mixtures whose cyclic content or acyclic content cannot be controlled easily to provide a product mix that can improve the end-use performance for a given application. Still, other processes must decompose higher members of the series by recycle to the dimers and trimers. Cyclic species are desired for many applications. For example, hPIP content is useful in epoxy curing applications as well as in lube oil and fuel compositions. Yet, other processes produce hPIP at low yields or produce byproduct salts that must be disposed of. It would be desirable to have a process that could vary the cyclic/acyclic mixture of amines that could be customized for a given end-use application from readily available starting materials.